1. Field of the Invention
The present invention relates to a microwave packaging, particularly to a microwave packaging made of a flexible, heat-sealable laminate. The packaging is intended to accommodate a food during storage and heating in a microwave. The microwave packaging can be provided both as a single sales packaging or in combination with a wrapper packaging.
2. The Prior Art
To prepare a heated food, the microwave packaging, together with the food contained in it, has microwave energy applied to it in a microwave oven. In this connection, heating is based on absorption of the microwaves by the moisture contained in the food and/or by an additional, energy-absorbing susceptor. Rapid heating of prepared foods is supposed to be made possible with the microwave packaging. Furthermore, the quality, the appearance, and the progression of the cooking process of the food during heating is supposed to be influenced by the type of packaging.
Microwave packagings are known from the state of the art, in the most varied embodiments. For example, U.S. Pat. No. 4,927,991 describes a microwave packaging having an energy-absorbing susceptor as well as a grid that controls the intensity of the microwaves. The susceptor heats up greatly as a result of absorption of the microwaves, so that the food, for example a prepared ready-to-eat pizza, is heated indirectly by way of the susceptor. Through the use of the susceptor, high temperatures in the range of typically 160° to 180° are reached, and regions of a food having different water content can be heated to the same extent, in advantageous manner. The use of susceptors has proven itself useful for preparing foods that are crispy and crunchy. Carry-over cooking and browning are also made possible by means of indirect heating using susceptors.
However, disadvantages of such active packaging are great production effort and high production costs. In particular, the material of the packaging must have a high temperature resistance because of the strong heating of the susceptor, thereby greatly restricting the selection. Accordingly, comparatively rigid, thick-walled materials are usually provided. Because of the indirect heating of the food, there are efficiency losses due to heat losses, and these lead to an increased heating period in comparison with direct heating. Finally, the food is also subjected to significant changes during heating, due to the high temperatures. For example, a strong moisture loss is usually connected with carry-over cooking, whereby steam that is formed can escape through openings or valves of the microwave packaging. Thus, there is the risk that the food, while it does become crispy and crunchy, also becomes unpleasantly dry.
Against this background, it can be advantageous if the food to be heated up is essentially already completely cooked, and is merely heated up in the microwave.
In the case of a simple microwave packaging that is entirely formed from a plastic film and does not have a susceptor, the food accommodated in the packaging is heated directly. When this happens, steam forms, which penetrates to the outside and condenses both on the inner surface of the packaging, which is still cold, because of the lack of additional heating, or on the outside of the food. This leads to the result that the inside of the food becomes tough and the outside of the food becomes mushy. When using simple microwave packagings that are only formed from a plastic film, very non-uniform heating of the food is also frequently observed.
U.S. Pat. No. 7,141,770 B2 describes a microwave packaging that has an absorbent insert underneath the food. The absorbent insert is intended to absorb liquid that drips off and thus regulates the moisture content within the packing to a certain extent. Since the insert covers only a small region of the surface underneath the food, condensation of liquid on the other inner surface of the packaging as well as on the outside of the packaging cannot be avoided. For example, moisture can also condense above the food and drip onto the food.